20 
tural difficulties the river might have to 
contend with, but contents himself with the 
simple statement: ‘‘ The river had the right 
of way ; in other words, it was running ere 
the mountains were formed ; not before the 
rocks of which the mountains are composed 
were deposited, but before the formations 
were folded so as to make a mountain 
range.” Later he remarks: “ I reserve the 
subject for a more full discussion in my re- 
port on the geology of the Uinta moun- 
tains.’”’ In this report, however, I had been 
able to find no mention of the subject what- 
ever, and I had assumed that upon further 
study he had found the difficulties in the 
way of his theory too great to be explained 
away. 
My study of the region was made in the 
summer of 1871. Powell continued his 
during the years 1874 and 1875, after, at 
his request, I had explained to him my 
views as to the structure of the range. 
Upon the following facts with regard to 
its geology we are both agreed. The up- 
lift of the Uinta Arch commenced at the 
close of the Cretaceous. During Tertiary 
times there were deposited in the lakes, 
which washed either flank of the range, not 
less than 8,000 feet of sediments that were 
derived, in part, at least, from the degrada- 
tion of that Arch. 
Now, as my map shows, these Tertiary 
beds, overlapping in a nearly horizontal 
position the upturned and truncated edges 
of the various formations composing the 
original arch, reach altitudes of 9,000 and 
10,000 feet at various points along either 
flank of the western and higher portion of 
the range. The eastern portion of the 
range, through which the peculiarly wind- 
ing cafions of the Green River have been 
cut, has an elevation of only 7,500 to 8,500 
feet, a few of the higher points reaching 
9,000 feet, and in one case 9,297 feet. 
According to Powell’s theory, however, 
the river had determined its course before 
SCIENCE. 
[N. 8. Von. VI. No. 131. 
the uplift of the arch, and has continued to 
occupy the same bed to the present day. 
“The principal cafions through the moun- 
tains,”’ he says, ‘‘ had been carved nearly to 
their present depth before the last of these 
sediments were deposited.”’ 
What, then, became of the river while 
these 8,000 feet of Tertiary sediments were 
being deposited? It could hardly have 
continued its course at the bottom of the 
Tertiary lakes while the sediments were 
depositing. But if it ceased to flow during 
this time its bed must have been filled with 
sediments as well as the rest of the country, 
and when the lakes were finally drained, it 
is hardly conceivable that, in redetermin- 
ing its course across the 150 miles of Ter- 
tiary beds on the north side of the range, 
it should have attacked the flanks of the 
Uinta range, themselves partially buried, at 
exactly the same point it had entered be- 
fore. 
There are many other features that re- 
quire explanation before Powell’s hypo- 
thesis can be accepted, one of which Pro- 
fessor Davis has pointed out in the Brown’s 
Park depression, a longitudinal valley 40 
miles long and 5 to 6 miles wide, open only 
at its eastern end, and nearly in the axis of 
the range. It is supposed to have been 
formed by engulfment, and has twice been 
occupied by Tertiary waters, once in 
Eocene, and once in Miocene or later times. 
How the river kept its course (which 
three times wantonly leaves the open valley 
to cut cafions in its hard walls) through 
all these vicisitudes, would seem to require 
amore direct explanation than that ‘The 
river preserved its level, but the mountains 
were lifted up, as the saw revolves on a 
fixed pivot, while the log through which it 
cuts is moved along.” 
Inasmuch as the promised discussion did 
not appear, I have recently asked Major 
Powell to explain to me his conception ot 
how these things could have been accom- 
